Pharmaceutically active agents are generally formulated as solid or liquid dosage forms for administration. Such dosage forms generally comprise the active agent combined with excipients to form materials that may be conveniently and reliably administered to a patient in need of such therapy, and following administration, the active agent is absorbed and distributed in the patient in a way that leads to good efficacy and safety.
For example, when a low-solubility active agent is dosed orally, it is sometimes desired to form a solid amorphous dispersion of the active agent and a polymer in order to enhance the absorption of the active agent. One reason for forming solid amorphous dispersions is that the aqueous dissolved active agent concentration of a poorly aqueous soluble active agent may be improved by forming an amorphous dispersion of the active agent and a polymer. For example, Curatolo et al., EP 0 901 786 B1 disclose forming pharmaceutical spray-dried dispersions of sparingly soluble drugs and the polymer hydroxypropyl methyl cellulose acetate succinate (HPMCAS). Such solid amorphous dispersions of drug and polymer provide higher concentrations of dissolved drug in an aqueous solution compared with the drug in crystalline form. Such solid amorphous dispersions tend to perform best when the drug is homogeneously dispersed throughout the polymer.
In another example, an active agent is combined with a polymer and formed into nanoparticles, having an effective diameter of less than about 400 nm. Such nanoparticles can be used for a wide variety of delivery routes, including oral, injectable, ocular, and pulmonary delivery of the active agent.
For most non-oral delivery routes, it is desired that the excipients used in the formulation be at least biocompatible, or preferably biodegradable. However, many of the excipients used in oral formulations, and especially polymers, are not biodegradable or biocompatible. Those pharmaceutically acceptable polymers that are biodegradable or biocompatible often do not have the desired or required properties for effectively formulating the active agent into the desired form. For example, most polymers that can be safely used for parenteral delivery are highly water soluble. As a result, they are typically inappropriate for use in making aqueous suspensions of nanoparticles or other types of dosage forms such as long-acting depots.
What is desired is a pharmaceutical composition comprising an active agent and a polymer, wherein the polymer has improved properties that make the composition suitable for a wide range of applications.